engleski

Optical emission spectroscopy characterization of oxygen plasma during degradation of bacteria

Optical emission spectroscopy was applied for plasma characterization during sterilization of substrates contaminated with bacteria. The amount of cells in the range from 1010 to 106 of Escherichia coli or Bacilus stearothermophilus was carefully applied to glass substrates and exposed to oxygen plasma at different pressures between 30 and 200 Pa. Plasma was created in a glass discharge tube by an inductively coupled RF generator at the frequency of 27.12 MHz and output power of about 250 W. The electron temperature and plasma density were estimated with a double Langmuir probe. They were between 3 and 5 eV and 2 and 35 1015 m−3. Density of neutral oxygen atoms was measured with a catalytic probe, and was between 2 and 6 1021 m−3. Optical emission spectroscopy was performed with a low resolution spectrometer. The evolution of different spectral features was applied to monitor the sterilization process. The intensity of spectral lines or bands of different radicals formed in the experimental chamber due to interaction of oxygen plasma with bacteria showed well defined maxima corresponding to the most intensive etching of bacterial material. As a general rule, the intensity of the lines was increasing with increasing amount of bacteria. The tail of these spectral features after prolonged treatment depended on the concentration of bacteria too, what was explained by weak overlapping of bacteria deposited on substrates.

oxygen plasma; sterilization; bacteria

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